1. Field of the Invention
The invention is a device for smoothing out the ripple in the radiation pattern of a shaped beam antenna system employing a lens and a feed array having several feed elements. The invention has particular applicability to the transmission and reception of signals above 300 MHz, where the lens design is practical.
2. Description of the Prior Art
A prior art search was performed and uncovered the following U.S. patent references:
U.S. Pat. No. 3,737,909 is a technique for increasing the efficiency (gain) of a paraboloidal antenna system. The present invention, on the other hand, is directed to the smoothing of ripples within the pattern of a lens antenna system.
U.S. Pat. No. 4,090,203 is a system for selecting the power to be applied to each of a plurality of feed elements, and for selecting the spacing to be used between feed elements in a paraboloidal antenna system so as to attenuate sidelobes in such a system. The present invention is directed not to sidelobes but to the coverage area of a lens antenna.
U.S. Pat. No. 4,126,866 is a frequency sensitive surface which reflects all electromagnetic radiation at a designated frequency. The present invention, on the other hand, does not reflect all of the energy at a certain electromagnetic frequency, but rather reflects, absorbs, or changes the phase of only a certain spatial frequency component of the electromagnetic radiation.
U.S. Pat. No. 4,021,812 is directed to modifying the radiation pattern outside the coverage area of an antenna, whereas the present invention modifies the radiation pattern within the coverage area.
Other patents disclosed were U.S. Pat. Nos. 3,214,760, 3,392,393, 3,698,001, and 4,125,841.